1. Field of the Invention
The invention relates to a method and apparatus for recognizing and reading magnetic ink characters and other magnetic patterns printed on a document and, is specifically concerned with improved techniques for magnetic character recognition in multipurpose point-of-sale ("POS") devices.
2. Description of the Related Art
Use of magnetic ink character recognition devices to discriminate checks and other forms of commercial paper printed with magnetic ink characters has become widespread within the world financial community. In addition to cash and credit cards, personal checks are widely used for shopping as well as paying bills. The face of such checks are typically printed with the check writer's account number, check serial number, routing information and other information using magnetic ink characters conforming to the well-known Magnetic Ink Character Recognition Standard to enable both electromechanical and human dissemination of the so-encoded data. This information can then be read to, for example, determine check validity and avoid fraud or counterfeiting.
This has led to the use of devices for reading magnetic ink characters in retail store POS stations and check-out counters. Many of these magnetic ink character recognition devices use DC motors to transport the personal check slips by a magnetic head for magnetic ink character recognition.
The use of such magnetic ink character recognition (MICR) devices at individual POS stations necessitates devices that are compact, easy to operate, and extremely reliable. After a personal check has been passed through the MICR reader for magnetic ink character recognition, it is necessary to load the check into a printer for indorsement printing, for example. This has led to the development of compound POS printers comprising both MICR reader and conventional POS printer functions such as that shown in FIG. 1.
The compound POS printer shown in FIG. 1 incorporates an MICR reader function into a printer that holds two rolls of paper, one of which is used for journal printing and the other for printing receipts, and can print to single slip forms inserted from the bottom of the apparatus. This type of compound POS printer is a compact, high functionality device that can automatically handle the multiple operations from MICR reading to indorsement required to process the personal check. This makes such devices suited for use in POS applications, and they are expected to be widely used in stores, hotels, and other commercial establishments.
One serious obstacle preventing more widespread adoption of compound POS has been the presence of undesirable amounts of magnetic noise during magnetic ink character reading caused by the printer transport mechanism. In dedicated MICR readers having only an MICR character reading function this problem is addressed by assuring sufficient distance between the magnetic head and the drive motor, which is the major source of magnetic noise, or by using a dc motor, which produces relatively little magnetic noise.
However, in the above-described compound POS printers, it is difficult to obtain sufficient distance between the motor and head while still accommodating routine recording operations. Providing a separate motor and drive system only for MICR character reading also increases device size as well as the complexity of the control circuitry involved, the total cost, and device weight. It is therefore desirable to share the transportation mechanism and other components used for printing. In this case, it is preferable to read the MICR characters while transporting the personal check past the magnetic head by means of a transportation mechanism that uses a pulse or stepping motor suitable for conventional printing operations. To accomplish this, however, some means of eliminating the magnetic noise from the pulse motor is required.
While magnetic noise can be conventionally suppressed by providing a magnetic shield between the pulse motor and magnetic head, it is difficult in a compact POS printer design to suppress magnetic noise to a sufficiently low level using such a shield. The condition of the MICR characters printed on personal checks can also vary as a result of soiling, folds, and the like on the check face, and noise during recognition must therefore be suppressed as much as possible in order to read MICR characters with a high recognition rate.